| Noble metal nanoclusters, consisting of a small number of atoms, provide a valuable link between metal atoms and nanoparticles as a new type of fluorescent nanomaterial. Noble metal nanoclusters possess a serial of advantages:small sizes, high emission rates, good stability, low toxity, good water solubility and biocompatibility, so they become the hot-spot recent years in biosensors, bioimaging, environmental protection, health care and many other fields. In this thesis, poly (cytosine)-templed silver nanoclusters are utilized as fluorescence sensors for the detections of glucose and uric acid, and poly (cytosine)-templed silver nanoparticles as antibacterial material for killing bacteria. The main contents are as follows:(1) Synthesis of poly(cytosine)-templated silver nanoclusters and construction of fluorescent biosensor for glucose. (Chapter 2)In this chapter, water soluble silver nanoclusters (AgNCs) were synthesized through a simple and nontoxic poly(cytosine)DNA-templated method. The influence of buffers, pH and reaction time were discussed. Under optimized conditions, the poly(cytosine)-templated silver nanoclusters (C-AgNCs) show an average size of 2.5 nm and a stable fluoresence emission peak at 565 nm. The fluorescence of the C-AgNCs could be sensitively quenched by H2O2 with a linear concentration range of 5～300μM with a detection limit of 0.67μM. Then the C-AgNCs combined with glucose oxidase were used to construct fluorescent biosensor for glucose. Under optimized conditions, detection of glucose has a linear concentration range of 0.05～50 μM with a detectable minimum concentration of 0.05μM. The fluorescent biosensor was further used for the detection of the glucose in serum. The results were consistent with that of blood-glucose meter.(2) Poly (cytosine)-templated siver nanoclusters as fluorescent biosensor for highly sensitive and fast detection of uric acid. (Chapter 3)Uric acid (UA) is an important biomarker in urine and serum samples for early diagnosis. This chapter reports a fluorescent biosensor based on silver nanoclusters (C-AgNCs) and uricase for the highly sensitive and fast detection of UA. The strong fluorescence of the C-AgNCs prepared from poly (cytosine) nucleotides templates could be sensitively quenched by trace amount of H2O2, which produced from oxidation reaction of UA catalyzed by uricase. This biosensor exhibits two linear ranges as 50 nM～10μM and 50～400μM, with a detection limit of 50 nM. The sensitivity of the biosensor is considerably improved compared with the methods reported in the literature. Furthermore, the detection ability of uric acid in serum samples is confirmed and this C-AgNCs-based uric acid biosensor shows good promise of practical application.(3) Preparation of water-soluble silver nanoparticles and its antibacterial properties. (Chapter 4)Poly (cytosine)-templated silver nanoparticles (DNA-AgNPs) were synthesized by liquid phase reduction with NaBH4 as the reductant. The structure and property of the DNA-AgNPs were investigated by transmission electron microscopy (TEM), dynamic light scattering (DLS) and fluorospectrophotometer. The antibacterial activity of the water-soluble DNA-AgNPs against Escherichia coli (E. coli) and Bacillus subtilis (BS) was investigated by minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) method. The results show that the as-synthesized DNA-AgNPs have a spherical structure and the average diameter of the DNA-AgNPs is about 50nm and have good dispersibility and solubility in water over a long period of time. Besides, the DNA-AgNPs exhibit good antibacterial properties against E. coli and B.S. By simple and mild preparation method, DNA-AgNPs are potentially a new type of antibacterial. |
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